Modelling depth to groundwater level using SEBAL-based dry season potential evapotranspiration in the upper Molopo River Catchment, South Africa

Abstract

Groundwater has emerged to be a formidable poverty reduction tool in many developing countries because it can be distributed to poor communities far more cheaply, quickly and easily. This study investigated the applicability of dry season potential evapotranspiration (ETp) in modelling depth to groundwater level in the upper Molopo River catchment. Landsat-5 TM images for the years 1995 and 2005, and Landsat-8 OLI for the year 2015 were obtained from USGS website. Meteorological data for 1995, 2005 and 2015 were obtained from the South African Weather Services, and were integrated with satellite data for the corresponding years when estimating ETp. ETp for each year was estimated using Surface Energy Balance Algorithm for Land (SEBAL). Depth to groundwater level data, recorded in July 2015, were obtained from the Department of Water and Sanitation of South Africa. Linear regression analysis was used to determine the relationship between ETp and groundwater. The results revealed variations in spatio-temporal trends of ETp. A gradual decline in ETp was noted across the study area between 1995 and 2015. Variations in depth to groundwater level was also noted in the study area. Finally, high ETp was noted in sites of shallow water table and low ETp in sites of deep water tables. Therefore, the assessment of ETp and their changes on catchment scale is crucial to planning and management of groundwater of the particular catchment. Keywords: Groundwater, Potential evapotranspiration, SEBAL, Linear regression analysis